“Soft” electronic products fabricated via new cost-effective processes will require the discovery/implementation of key materials components as well as unconventional routes to efficient device assembly. Organic molecular and polymeric (semi)conductors and gate dielectrics are among the most important materials for development of this new technology since they are needed for fabricating thin-film transistors (TFTs)—an essential electronic device component. Therefore, successful TFT materials candidates should be deposited via inexpensive methodologies such as spin-coating, casting, and printing and at low temperature to ensure compatibility with plastic substrates. Furthermore, for complementary circuit applications both p- (hole-) and n-type (electron-transporting) semiconductors should perform optimally with the same gate dielectric material. During the past few years, a number of efficient p- and n-type semiconductors for organic TFTs (OTFTs) have been discovered.
More recently, research in this area has attacked the problem of large OTFT operating voltages by developing new gate dielectric materials, most of which are fabricated into very thin films. However, because OTFT structures are invariably based on very thin dielectrics, the gate is unpatterned, and the issue arises as to whether it is possible to deposit nanoscopic dielectric films on patterned gate line (for practical TFT circuitry) and yet preserve excellent insulating characteristics, high dielectric strength, smooth surface morphology—to yield functional OFETs. This issue is even of greater importance for printed conductors, which are much thicker than conventional vapor-deposited metals. Accordingly, the search continues in the art for new device structures and methods of fabrication to better utilize recent material developments.